An ethylene-α-olefin copolymer has been conventionally used for various applications.
For example, since a crosslinked foamed product using an ethylene-α-olefin copolymer is high in mechanical strength and is lightweight and flexible, it is used for interior and exterior materials for construction, automotive parts such as door glass run channels and the like, packaging materials, daily necessities, and others. Here, since a non-crosslinked foamed product is weight-reduced but is low in mechanical strength, when it is used for the applications as described above, the mechanical strength has been improved by subjecting a resin to crosslinking reaction to bond molecular chains in the foamed product.
In addition, the crosslinked foamed product of a resin is also used for footwears or footwear parts, for example, soles (mainly, midsoles) of sports shoes or the like. The reason is that it is required for footwears or footwear parts to have a condition in which they are lightweight and have a mechanical strength and rebound resilience high enough to inhibit deformation caused by long-term use and to withstand severe use conditions.
It is widely known that crosslinked foamed products of ethylene-vinyl acetate copolymers are conventionally used for shoe soles. However, since the crosslinked foamed products, which are molded using the ethylene-vinyl acetate copolymer composition, have a high specific gravity and a high-compression set, when used, for example, for shoe soles, there is a problem that the soles are heavy and compressed by long-term use and the mechanical strength such as rebound resilience and the like is losing.
In Patent Documents 1 and 2, there are described inventions, respectively, relating to a crosslinked foamed product using an ethylene-α-olefin copolymer and a crosslinked foamed product using a mixture of an ethylene-vinyl acetate copolymer and an ethylene-α-olefin copolymer. However, these inventions improve low specific gravity properties and low compression set properties, but do not provide sufficient performance. In addition, in Patent Document 3, there is described an ethylene-α-olefin-specific non-conjugated polyene random copolymer. However, it becomes clear from the studies of the present inventors that there is a room for improvement from the standpoint of providing a foamed product with consistent quality and having a low specific gravity and a low compression set (CS). For this reason, there is a demand for the appearance of a foamed product with consistent quality and having a low specific gravity and a low compression set (CS) and an ethylene-α-olefin copolymer and a composition having high crosslinking properties which may be used for the production of the foamed product.
In addition, the present applicant has proposed a resin composition containing an ethylene-α-olefin copolymer and an ethylenic copolymer rubber (see Patent Document 4). When the resin composition is used as a raw material for coating an electric wire, it is disclosed that the resin composition is more excellent in balance between weather resistance and mechanical strength, compared to the case where a copolymer containing an ethylene-propylene-diene rubber is used as a raw material for coating an electric wire (for example, see Patent Document 5). However, a further improvement has been demanded in the balance between weather resistance and mechanical strength when the resin composition is used for wire coating.
On the other hand, an olefinic thermoplastic elastomer is used for automotive parts, industrial machine parts, electronic and electric device parts, building materials and the like as an alternative of a vulcanized rubber. However, there is a demand for a material having excellent tensile strength, breaking elongation and rubber elasticity. For example, it is known that a molded article having a low-temperature property and tensile strength, which is improved as compared with a conventional vulcanized-rubber, is produced by the use of a composition containing a crystalline polyolefin resin and an ethylene-α-olefin-non-conjugated polyene copolymer rubber prepared using a metallocene catalyst (see patent Document 6). However, there has been a demand for the appearance of a thermoplastic elastomer capable of producing a molded article that is more excellent in balance between mechanical strength and toughness such as tensile elongation and the like.    Patent Document 1: Japanese Patent Application Laid-Open No. H09-501447    Patent Document 2: Japanese Patent Laid-Open Publication No. H11-206406    Patent Document 3: Japanese Patent Laid-Open Publication No. H11-5818    Patent Document 4: Japanese Patent Laid-Open Publication No. 2006-249136    Patent Document 5: Japanese Patent Laid-Open Publication No. H08-127680    Patent Document 6: Japanese Patent Laid-Open Publication No. H09-12790